Histochemical study on rat tear film and ocular surface epithelial cells

Curr Eye Res. 1998 Jun;17(6):642-9.


Purpose: To investigate the histochemistry of the tear film, conjunctival goblet cells and corneal superficial epithelial cells by an in vivo cryofixation with the freeze-substitution method.

Methods: Following rapid freezing of the eyeballs by an isopentane-propane mixture cooled by liquid nitrogen directly, the specimens were freeze-substituted and then embedded in Lowicryl K4M resin at low temperature, or in epoxy resin for histochemical study, using light and transmission electron microscopy.

Results: The tear film was weakly positive with periodic acid-Schiff staining, but negative with alcian blue at pH 2.5 or pH 1.0 and high iron diamine staining. Conjunctival goblet cells were positively stained by all these techniques. There was a gradually weakening staining intensity of mucus from the goblet cells to the conjunctival surface. With the periodic acid-thiocarbohydrazide-silver protein method the tear film was weakly stained, while glycocalices, vesicles, glycogen in epithelial cytoplasm and the mucus secretory granules of goblet cells were all intensely stained.

Conclusions: The tear film consists mainly of dilute mucus and contains either neutral or acid glycoproteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acrylic Resins
  • Alcian Blue
  • Animals
  • Conjunctiva / chemistry*
  • Conjunctiva / cytology
  • Conjunctiva / ultrastructure
  • Cryopreservation
  • Epithelium, Corneal / chemistry*
  • Epithelium, Corneal / cytology
  • Epithelium, Corneal / ultrastructure
  • Freeze Substitution
  • Glycogen / analysis
  • Glycoproteins / analysis*
  • Histocytochemistry
  • Lacrimal Apparatus / chemistry
  • Lacrimal Apparatus / cytology
  • Mucus / chemistry*
  • Mucus / cytology
  • Periodic Acid-Schiff Reaction
  • Rats
  • Rats, Wistar
  • Tears / chemistry*


  • Acrylic Resins
  • Glycoproteins
  • Lowicryl 4KM resin
  • Glycogen
  • Alcian Blue